This invention relates generally to a system in which a primary terminal normally handles data interchange or communications among a plurality of secondary terminals and in which an alternate terminal is provided and has as one of its functions that of acting as an "alternate primary terminal" to handle the communications among the plurality of secondary terminals, for example; this invention relates specifically to a communications switch which automatically enables the alternate primary terminal to function as the primary terminal when the primary terminal is inoperative for one reason or another.
One of the known ways in which the switching from the primary terminal to the alternate primary terminal was effected in a system as generally described was to wait until the primary terminal was inoperative as indicated by, for example, a display message indicating the inoperative state on one of the secondary terminals. An operator at the secondary terminal would have to go to the primary terminal which might be located in a supervisor's office in order to find out what was wrong with the system. The primary terminal might indicate, through its associated display, that it was unable to communicate with the secondary terminal. Thereafter, the operator would actuate a manually-operated switch which caused the alternate primary terminal to function as the primary terminal and the "now downed primary terminal" to function as the alternate primary terminal to permit communications to be resumed.